> Scaling back on the original intent, then, could we expose to Lisp a way to create a chrome-less frame, presumably in just the same way as the tooltip code does it? Something like `remove_frame_chrome(frame *f)`, which one would call before making a frame visible.

This will definitely work on X.  Basically an X window manager takes over a window when it gets mapped (becomes visible).  But I'm not sure if the procedure is necessary on other platforms.

I think it'd be better if we can control this directly by feeding `make-frame' a new frame parameter.